Heat sink



FIG. 1 is a perspective view of a heat sink, taken from the right forward side;

FIG. 2 is a top plan view of the heat sink of FIG. 1;

FIG. 3 is a bottom plan view of the heat sink of FIG. 1;

FIG. 4 is a front elevational view of the heat sink of FIG. 1, the rear elevation view being a mirror image thereof; and,

FIG. 5 is a side elevational view of the heat sink of FIG, 1, the opposite side being a mirror image thereof.

Portions of FIGS. 1-5 that are shown as broken lines are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a heat sink, as shown and described. 